Griphook agrees to help them break into Bellatrix Lestrange’s Gringotts vault, but he demands the Sword of Gryffindor as payment. This puts Harry and his friends in a bind, because if they refuse, they’ll never get into the vault to look for a Horcrux, but if they give up the sword, they’ll have no way to destroy any Horcrux they find. Harry decides to trick the goblin, telling him he can have the sword after they break into the vault, but not specifying how long after. Feeling somewhat guilty, Harry gives his promise to Griphook, and for several weeks they plan the break-in.
Lupin arrives at the cottage with the news that Tonks has had her baby. He asks Harry to be the godfather, and Harry agrees.
Before Harry and the others embark on their mission, Bill takes Harry aside. He does not know what Harry is planning to do or how Griphook is involved, but he warns Harry to be careful of goblins. He says that goblins are deeply distrustful of wizards, believing that wizards do not respect agreements involving treasure and tend to trample on goblin rights. He explains that goblins believe manufactured items belong to the maker, and that ownership of goblin-made goods should not pass from wizard to wizard but should revert to the goblins after the first owner’s death. He warns Harry of the dangers of reneging on a deal with a goblin.
To break into Gringotts, Hermione disguises herself as Bellatrix Lestrange and changes Ron’s appearance so he’s unrecognizable. With Harry and Griphook under the Invisibility Cloak, the four go to Diagon Alley, where they see witches and wizards begging in the streets, deprived of their wands by the Ministry.
A Death Eater named Travers stops Hermione/Bellatrix, noting that he’d heard she’d been confined to her house and lost her wand, but Hermione dismisses his questions contemptuously, in a good imitation of Bellatrix’s manner. Unfortunately, Travers is going to Gringotts too, and they enter the bank together.
The first security obstacle they face is Probity Probes—rods that detect the presence of Concealment spells and magical items. Harry sneaks up in his cloak and zaps the guards working the probes with spells of Confusion.